1. Field of the Invention
The present invention relates to a positive working resist composition which causes a reaction upon irradiation with actinic rays or radiation to change properties, to a pattern forming method using the positive working resist composition and to a compound to be used in the positive working resist composition. In more detail, the invention relates to a positive working resist composition which is used in a manufacturing step of a semiconductor device such as IC, in the manufacture of a circuit board of a liquid crystal, a thermal head and the like and other fabrication steps, lithographic printing plates and acid-curable compositions, to a pattern forming method using the positive working resist composition and to a compound to be used in the positive working resist composition.
2. Description of the Related Art
In recent years, in an integrated circuit, the degree of integration is increasing more and more. In the manufacture of a semiconductor substrate such as VLIS, processing of an ultrafine pattern composed of a line width of not more than a half-micron has become necessary. In order to fulfill its necessity, the wavelength to be used in an exposure apparatus which is used for the photolithography is shortened more and more, and nowadays, it is studied to use an excimer laser beam (for example, XeCl, KrF and ArF) having a short wavelength among far ultraviolet lights. As a material which is used for the pattern formation of lithography in this wavelength region, a chemical amplification system resist is exemplified.
In the case where a KrF excimer laser is used as an exposure light source, since a resin having small absorption chiefly in a region of 248 nm and having poly(hydroxystyrene) as a basic skeleton is used as the major component, a satisfactory pattern with high sensitivity and high resolution is formed, and a satisfactory system is revealed as compared with a related-art naphthoquinone/novolak resin system.
On the other hand, in the case where a light source having a shorter wavelength, for example, an ArF excimer laser (193 nm) is used as an exposure light source, since a compound having an aromatic group exhibits large absorption essentially in a 193 nm region, it was not sufficient even in the foregoing chemical amplification system.
For that reason, a resist used for ArF excimer laser containing a resin having an alicyclic hydrocarbon structure has been developed.
For example, JP-A-2003-167347 and JP-A-2003-223001 describe a composition containing a resin having a polycyclic acid-decomposable repeating unit and a non-acid-decomposable repeating unit. Such a resin is a chemical amplification type resist having a protective group which is dissociable by an acid and is instable against an acid. Under a circumstance that the realization of a much finer resist pattern is demanded, however, it has become difficult to obtain sufficient resist performance only by using such a protective group singly.
Then, for example, JP-A-11-119434 discloses a positive working resist composition containing a resin having two kinds of repeating units having an acid-decomposable group.
Also, as described in JP-A-2005-37893, JP-A-2001-98034 and JP-A-2000-214587, a resist polymer in which a crosslinking site which is dissociable by an acid is introduced into a side chain of a resin containing a repeating unit having an acid-dissociable protective group is studied.
This resides in the matter that when a crosslinking bond is cleaved by an acid catalyst, a dissolution contrast between an exposed area and an unexposed area is enhanced. However, in polymerization of the polymer, a bifunctional monomer such as diacrylates is used, and a crosslinking reaction in a side chain of a high-molecular weight chain follows. Therefore, the molecular weight distribution of a formed polymer is extremely large, the solubility is poor, and a polymer having an ultrahigh molecular weight is easily formed. Thus, there was a problem that even after the decomposition with an acid, a sparingly soluble high-molecular weight component which is hardly dissolved in an alkaline developer is present, whereby pattern collapse is easily generated due to the presence of this foregoing substance.
Also, as described in JP-A-2001-98034, in the case where a crosslinked polymer having a crosslinking site having an acetal skeleton which is instable against an acid in a high-molecular weight side chain thereof is used as a resist polymer, there was a tendency that the storage stability is poor because of very high sensitivity to an acid.
On the other hand, for example, as described in JP-A-2006-91762 and WO 2005/085301A1, a positive working photosensitive resin having an acid-dissociable structure introduced in a high-molecular weight principal chain thereof is proposed. Though such a proposal is a proposal for solving the foregoing problem of a side chain crosslinking type polymer, its effect was still insufficient.